Processing time, computational load, and stimulus strength interact in perceptual decisions. Studies with non-human primates and rodents have demonstrated that perceptual decisions are guided by stimulus processing as well as cognitive factors, such as decision confidence. For both olfactory and visual discrimination, mice and rats demonstrate a trade-off between accuracy and speed, which is mediated by the level of difficulty and amount of sampling time. In order to investigate the relationship between performance and response time for an discrimination task in which rats controlled trial initiation, response frequency and accuracy were measured across reaction time (RT). Rats discriminated visual patterns consisting of solid-lines (low computational load) or dot grids (high load). Stimulus contrast and duration were varied across conditions. Results indicated a peak function across RT with two phases: an earlier component where accuracy improved to a peak level, followed by a later component where accuracy remained stable or declined. For the earlier phase, reduced salience slowed processing with higher computational load. Unexpectedly, peak performance with highly salient stimuli occurred more quickly with higher computational load. For the later phase, accuracy did not benefit from longer RT, but instead progressively declined. Pre-peak characteristics suggest that accuracy benefits from increased stimulus processing time and is consistent with computational models of progressive accumulation of stimulus information. Post-peak characteristics may reflect factors associated with perceptual decision, such as uncertainty, which delays committing to a response. Results thereby suggest separate effects of stimulus processing and perceptual decision on discrimination accuracy across RT.

Perceived global organization of visual patterns is based upon the aggregate contribution of constituent components. Patterns constructed from multiple sources cooperate or compete for global organization. An investigation was made here of interactions between two interspersed element sets on global orientation. It was hypothesized that each set would operate as an integrated unit, and contribute independently to global orientation. Participants viewed a 10 × 10 array of Gabor patches, and indicated the predominant orientation of the array. In Experiment 1 all elements were rotated. Rotation up to 23° had little effect, whereas greater rotation produced a progressive shift on global orientation. In Experiment 2 a proportion of elements remained aligned while remaining elements were rotated. Embedding a proportion of aligned elements stabilized global orientation, which was dependent upon the proportion of aligned elements. Specifically, with 20% alignment, global orientation was similar to rotating all elements, whereas 80% alignment strongly biased perception towards aligned elements. The stabilizing effect varied with rotation of the second element set. Across levels of rotation, alignment effects rose to a peak then declined as element sets became orthogonal. In Experiment 3, each element set was rotated independently. Independent rotation of both sets altered global orientation, compressing the psychometric function for the single-element condition. Together, for interspersed element sets with explicit orientations, each set does not contribute independently to global orientation. Instead, element sets interact, where the contribution of one set, presented at a fixed rotation and fixed proportion, varies with the change to the second set.

Introduction Impaired perceptual organisation in schizophrenia has been repeatedly described in clinical and research literatures. It has also been associated with problems in more complex aspects of visual function, including visuospatial and visual cognitive test performance. Two therapeutic interventions were developed here that target perceptual organisation: (1) Computer-based training, which emphasized stimulus-driven processing (bottom-up approach), and (2) Instrumental Enrichment therapy, which is a therapist-guided interactive learning method (top-down approach). Methods Twenty-eight patients diagnosed with schizophrenia or schizoaffective disorder participated in a 12-week programme. For both forms of interventions, task difficulty increased progressively, based upon successful performance. The third group of patients, which served as controls, received a similar therapeutic intervention that did not include a perceptual organisation component. Before and after intervention, participants received tests of perceptual organisation, as well as a battery of neuropsychological tests. Results Results indicate that both forms of intervention improved perceptual organisation ability relative to the control condition. In addition, the improvement was found for select neuropsychological tests, although the pattern of improvement did not favour capacities more closely associated with visual organisational or visuospatial function. Conclusions Together, results demonstrate the effectiveness of new remediation protocols that target mid-level visual processing, which generalized to select visual cognitive functions.

Mechanisms underlying perceptual grouping serve to bind stimulus components that are contained within grouped patterns. In order to examine the time course of grouping development, grids of spatially isolated dots were followed by pattern masks across a range of SOA. Subjects indicated the predominant perceived grouping of the dot patterns. Masks either spatially superimposed target elements (element mask), or superimposed elements as well as paths among elements (connection mask). Element masks thereby disrupted processing of target elements, while connection masks additionally disrupted representations in regions among elements. It was found that element masks disrupted grouping 12ms after target offset, after which masks had no effect. Connection masks disrupted grouping up to 47ms following target offset. Results suggest grouping mechanisms access the afferent signal for a brief period early in processing, after which binding formation proceeds for an addition 35ms. Shortening connection mask duration to 12ms enhanced performance during a brief temporal window within the interference period. For each set of conditions, target elements were visible during the time frame in which stimulus patterns could not be perceptually grouped. Full-field checkerboard masks degraded discrimination similarly as connection masks, although were more effective in disrupting discrimination with an SOA of 24 and 36ms. Degrading stimulus organization progressively extended the time scale for each masking effect. For the grouping of low-level stimulus features tested here, results support a model in which afferent signals are accessed early, followed by progressive binding among grouped elements. Effect of shortening connection masks may reflect incomplete disruption of target processing, or possibly re-entry of stimulus representations by feedback from higher processing areas.

Training on visual tasks improves performance on basic and higher order visual capacities. Such improvement has been linked to changes in connectivity among mediating neurons. We investigated whether training effects occur for perceptual grouping. It was hypothesized that repeated engagement of integration mechanisms would enhance grouping processes. Thirty-six participants underwent 15 sessions of training on a visual discrimination task that required perceptual grouping. Participants viewed 20 × 20 arrays of dots or Gabor patches and indicated whether the array appeared grouped as vertical or horizontal lines. Across trials stimuli became progressively disorganized, contingent upon successful discrimination. Four visual dimensions were examined, in which grouping was based on similarity in luminance, color, orientation, and motion. Psychophysical thresholds of grouping were assessed before and after training. Results indicate that performance in all four dimensions improved with training. Training on a control condition, which paralleled the discrimination task but without a grouping component, produced no improvement. In addition, training on only the luminance and orientation dimensions improved performance for those conditions as well as for grouping by color, on which training had not occurred. However, improvement from partial training did not generalize to motion. Results demonstrate that a training protocol emphasizing stimulus integration enhanced perceptual grouping. Results suggest that neural mechanisms mediating grouping by common luminance and/or orientation contribute to those mediating grouping by color but do not share resources for grouping by common motion. Results are consistent with theories of perceptual learning emphasizing plasticity in early visual processing regions.

Changes in target visibility may be produced by additional stimulus elements at adjacent locations. Such contextual effects may reflect lateral interactions of stimulus representations in early cortical areas. It has been reported that the organization of orientation preference found in primates and cats visual cortex differs from that found in rodents, suggesting functional distinctions across species. In order to examine effects of lateral interactions at a perceptual level, contrast sensitivity in rats was measured for Gabor patches masked by two additional patches. Rats responded to target onset, and perceptual indices were based upon reaction time distributions across levels of luminance contrast. It was found that contrast sensitivity of targets without lateral masks corresponded to levels previously reported. For all measurements, the presence of sustained lateral masks systematically reduced sensitivity to targets, demonstrating interference by adjacent elements across levels of contrast. Effects of mask orientation or separation were not observed. These results may reflect reported non-systematic topography of orientation tuning across the cortex in rodents. Results suggest that intrinsic lateral connections in early processing areas play a minimal role in stimulus integration for rats.

The use of contextual information may be explored with infographics (informational graphics). Infographics is described as a combination of text, visual pictures, and graphs to demonstrate data, information and knowledge, as well as convey information through visual storytelling. Comprehending infographics has been associated with several cognitive functions, including attention, visuospatial perception, and visual working memory, as well as perception of holistic characteristics, a process termed Gestalt Thinking. The study described here aimed to develop an assessment tool of context processing by using infographics at different perceptual and cognitive levels. Observers viewed complex images and were asked specific questions about information contained within the image. Level 1 test items contained relationships among basic stimulus features, such as color and luminance, which required perceptual comparison and reasoning. Level 2 test items contained conceptual relationships among stimulus components, which required deductive reasoning. Performance was indexed as the level of feature disparity, where critical visual information was progressively made more salient. Assessments of verbal comprehension (vocabulary and similarity) and perceptual reasoning (block design and matrix reasoning) was based upon a standardized test (WASI II). Results indicated that unlike Level 1 infographics, a significant positive correlation existed between Level 2 infographics and matrix reasoning, which involves fluid intelligence, knowledge of part-whole relationships, and perceptual organization (Spearman rs=.897, p< .05). Unexpectedly, a significant negative correlation existed between Level 2 infographics and the similarities subtest, which involves crystalized intelligence and verbal concept formation (rs =-.901, p< .001). Results indicate that comprehension of Level 2 infographics, which rely on global relationships, is enhanced by visuospatial and perceptual organization ability, but weakened by greater ability in focusing on specific concepts. Results support a model of contextual processing that emphasizes global relationships and deemphasizes attention focus on image components. Meeting abstract presented at VSS 2017

For ambiguous stimuli, complex dynamics guide processes of perceptual grouping. Previous studies have suggested two opposing effects on grouping that are produced by the preliminary stimulus state: one that enhances grouping towards the existing structure, and another that opposes this structure. To examine effects of the preliminary state on grouping directly, measurements were made of perceived grouping of dot patterns that followed a visual prime. Three stimuli were presented in sequence: prime, target, and mask. Targets were composed of an evenly spaced dot grid in which grouping was established by similarity in luminance. Subjects indicated the dominant perceived grouping. The prime either corresponded to or opposed the prevailing organization of the target. Contrary to the hypothesis, solid-line primes biased grouping away from the structure of the prime, even when the prevailing organization of dot patterns strongly favored the primes' structure. This effect occurred, although to a lesser extent, when primes did not occupy the same location of targets, but were presented in a marginal area surrounding the grid. Priming effects did not occur for primes constructed of dot patterns. Effects found here may be attributed to a forward masking effect by primes, which more effectively disrupts grouping of patterns matched to the prime. Effects may also be attributed to a type of pattern contrast, in which a grouped pattern dissimilar to primes gains salience. For the pattern contrast model, the partial activation of multiple grouped configurations is compared to the pattern of the solid-line primes.

Across the visual field, progressive differences exist in neural processing as well as perceptual abilities. Expansion of stimulus scale across eccentricity compensates for some basic visual capacities, but not for high-order functions. It was hypothesized that as with many higher-order functions, perceptual grouping ability should decline across eccentricity. To test this prediction, psychophysical measurements of grouping were made across eccentricity. Participants indicated the dominant grouping of dot grids in which grouping was based upon luminance, motion, orientation, or proximity. Across trials, the organization of stimuli was systematically decreased until perceived grouping became ambiguous. For all stimulus features, grouping ability remained relatively stable until 40°, beyond which thresholds significantly elevated. The pattern of change across eccentricity varied across stimulus feature, in which stimulus scale, dot size, or stimulus size interacted with eccentricity effects. These results demonstrate that perceptual grouping of such stimuli is not reliant upon foveal viewing, and suggest that selection of dominant grouping patterns from ambiguous displays operates similarly across much of the visual field.

Top-down influence over short timescales (e.g. shape priming) has been shown to greatly improve success on high difficulty visual integration tasks by increasing salience, and over longer timescales, visual integration task training has resulted in enhanced visual integration performance. However, the possible benefit for task performance from combining the more immediate influence of shape priming with task training has not been explored. The aim of the present study was to determine if training in contour integration with added shape priming cues would improve performance on a contour integration task that has well-established psychometric properties. Subjects first briefly viewed a series of Gabor element displays with embedded contours forming shapes with the task of indicating which direction the shape was pointing (up, down, left, or right). A baseline threshold for target shape recognition was established. Task difficulty was determined by amount of jitter in orientation of the embedded contour elements. Perceptual threshold was established utilizing a staircase procedure. Subjects were then randomly assigned to training either with contour priming or without contour priming for 30 minutes a day, starting after baseline assessment, for a total of three consecutive days. After training on day 3, perceptual threshold was measured utilizing the same procedure as used at baseline. Using a two-way repeated measures analysis of variance it was established that both groups showed a significant decrease in perceptual threshold from baseline to post training assessment, but the effect of priming was not significant. These findings suggest that the top-down influence of shape priming does not modulate perceptual learning associated with visual contour integration training. Meeting abstract presented at VSS 2014

For complex, natural scenes, which contain multiple sources of visual information, high-order visual cognition relies on accurate organization of stimulus components. Perceptual organization is based upon stimulus metrics as well as top-down factors, including contextual cues and familiarity. Gestalt principles, such as common luminance, color, and surface texture, or good continuation of contrast borders, allow segregation and integration of elements across broad areas and occluded regions. It was hypothesized that component visual features, specifically color, high- and low-spatial frequencies, and surface information, each contribute significantly to perceptual organization of natural scenes. To test this, 34 participants viewed 60 briefly presented scenes, selected from a standardized data set, and categorized scenes as either forest, mountain, ocean coast, houses, highway, or city skyline. Each image was presented as a series of 19 trials, beginning with a highly occluded image, and progressively providing a greater percentage of the image. Performance was indexed as the occlusion level at which correct categorization stabilized. Five image filter conditions were examined: (1) original (unfiltered), (2) color filter (grayscale), (3) high-pass and (4) low-pass spatial frequency filter, and (5) surface field filter. In addition, images were presented either upright (familiar) or inverted (unfamiliar) for each filter condition. Results indicated that for upright as well as inverted images, high-pass, low-pass, and surface field filters significantly reduced performance (ANOVA, p <.05), whereas color filter has a modest affect performance. Greatest impairment was found for the low-pass and surface field filter conditions. These results indicate that coarse information, which reduces detail, is less beneficial in perceiving scene organization. In addition, information from edges needs to contain sufficient detail to facilitate perceptual organization of complex scenes. Meeting abstract presented at VSS 2014

Early visual processing in rats is mediated by several pre-cortical pathways as well as multiple retinal ganglion cell types that vary in response characteristics. Discrete processing is thereby optimized for select ranges of stimulus parameters. In order to explore variation in response characteristics at a perceptual level, visual detection in rats was measured across a range of contrasts, spatial frequencies, and durations. Rats responded to the onset of Gabor patches. Onset time occurred after a random delay, and reaction time (RT) frequency distribution served to index target visibility. It was found that lower spatial frequency produced shorter RTs, as well as increased RT equivalent of contrast gain. Brief stimulus presentation reduced target visibility, slowed RTs, and reduced contrast gain at higher spatial frequencies. However, brief stimuli shortened RTs at low contrasts and low spatial frequencies, suggesting transient stimuli are more efficiently processed under these conditions. Collectively, perceptual characteristics appear to reflect distinctions in neural responses at early stages of processing. The RT characteristics found here may thereby reflect the contribution of multiple channels, and suggest a progressive shift in relative involvement across parameter levels.

Evidence exists that damage to white matter connections may contribute to reduced speed of information processing in traumatic brain injury and stroke. Damage to such axonal projections suggests a particular vulnerability to functions requiring integration across cortical sites. To test this prediction, measurements were made of perceptual grouping, which requires integration of stimulus components. A group of traumatic brain injury and cerebral vascular accident patients and a group of age-matched healthy control subjects viewed arrays of dots and indicated the pattern into which stimuli were perceptually grouped. Psychophysical measurements were made of perceptual grouping as well as processing speed. The patient group showed elevated grouping thresholds as well as extended processing time. In addition, most patients showed progressive slowing of processing speed across levels of difficulty, suggesting reduced resources to accommodate increased demands on grouping. These results support the prediction that brain injury results in a particular vulnerability to functions requiring integration of information across the cortex, which may result from dysfunction of long-range axonal connection.

High-order cognitive functions require the integration of information across functionally related modules. This relationship suggests that cognitive ability is related to the efficiency and processing speed of basic integrative function. In order to examine individual differences for this relationship, we compared standardized tests of intelligence to visual perceptual grouping abilities, which represents a basic process of integration. Sixty participants discriminated perceived grouping of dot patterns based upon similarity in luminance. Psychophysical measurements were made of the functional limits and processing speed of grouping. We assessed cognitive abilities with the Wechsler Abbreviated Scale of Intelligence (WASI) and found that measures of grouping efficiency as well as speed varied considerably across subjects, indicating substantial individual differences at this relatively early level of visual processing. Faster grouping speed was associated with higher scores on all WASI subtests, whereas grouping ability, when not restricted by time, was associated only with the performance IQ components. These results demonstrate an association between a basic integrative function, in which cognitive and motoric factors were minimized, with measures of high-order cognition, which include both verbal and spatial cognitive components.

Are advantages in complex object perception that have been observed. in artists supported by advantages in more basic perceptual processes? To address this question, we compared artists and non-artists on a psychophysical task measuring perceptual grouping thresholds in order to test for group differences in sensitivity to perceptual grouping cues. Participants viewed grids of dots that could be perceptually grouped into a series of lines. The level of organization of stimuli was progressively reduced until perceived grouping was ambiguous. While artists were not observed to have an overall advantage relative to non-artists, non-artists exhibited sex differences in perceptual grouping sensitivity that artists did not. This suggests that the visual systems of male and female artists may be less differentiated than non-artist males and females.

Ketamine is a selective NMDA glutamate receptor antagonist that disrupts cognitive and behavioral function. Evidence exists that NMDA receptors play a role in lateral cortical connections, suggesting involvement in integrating information across the cortex. To investigate NMDA receptors' role in cortical integration at a perceptual level, psychophysical measures were made of perceptual grouping, which requires global analysis of neural representations of stimulus elements. Rats were trained to discriminate solid lines as well as patterns of dots that could be perceptually grouped into vertical or horizontal stripes. Psychophysical measures determined thresholds of perceptual grouping capacities. Rats receiving maximum subanesthetic doses of Ketamine discriminated solid patterns normally, but were impaired on dot pattern discrimination when greater demands were placed on perceptual grouping. These results demonstrate a selective disruption by Ketamine of visual discrimination that requires perceptual grouping of stimulus patterns. These results also provide evidence associating NMDA receptor-dependent neural mechanisms with context-dependent perceptual function.

The literature on university–industry (U–I) links has revealed many barriers that impede U–I technology transfer. A growing number of intermediary organizations, such as Technology Transfer Offices (TTOs), University Incubators (UIs), and Collaborative Research Centres (CRCs) have been established to mitigate such barriers. While the activities and effects of such intermediaries are frequently studied, conceptual understandings of how these organizations facilitate technology transfer are lacking. Our case study of nine Italian intermediary organizations shows that different types of intermediary organizations address the same fundamental issue of bridging the different logics of academia and industry in different ways. Based on a proximity approach, we develop a theoretical framework explaining how intermediary organizations can reduce cognitive, geographical, organizational, and social distance in U–I collaborations. Intermediary organizations address different proximity dimensions depending on the prior experience of academic and industrial actors and the nature of the knowledge that is transferred. In particular, TTOs focus more on improving cognitive and organizational dimensions, whereas UIs and CRCs attempt to reduce social and geographical distance.

Neural mechanisms mediating perceptual grouping serve to enhance associations among stimulus elements, thereby establishing unified forms. The goals of the present study were to identify cortical areas necessary to perceptually group spatially isolated elements, and to determine if these areas are distinct from regions necessary for the discrimination of simple, solid forms. Rats were trained to discriminate horizontal and vertical lines that were either solid or composed of disjunct elements in which discrimination required perceptual grouping by proximity. Psychophysical procedures established the limits at which proximity served as a cue for grouping. Following perceptual measurements, ablations were made to selective sites within visual cortex. Lesions within area 17 or area 18A, including their interface, produced nearly complete impairment of solid line discrimination as well as perceptual grouping at all levels of proximity, whereas lesions to areas 18 or the far lateral extent of area 18A no effect on these perceptual capacities. These results indicate that grouping by proximity requires early visual processing areas, and shares cortical areas necessary for simple pattern discrimination. These results suggest that mechanisms of grouping modify primary stimulus representations, constructing a pattern of activity functional similar to that elicited by solid forms.

Critical to vision research is the generation of visual displays with precise control over stimulus metrics. Generating stimuli often requires adapting commercial software or developing specialized software for specific research applications. In order to facilitate this process, we give here an overview that allows nonexpert users to generate and customize stimuli for vision research. We first give a review of relevant hardware and software considerations, to allow the selection of display hardware, operating system, programming language, and graphics packages most appropriate for specific research applications. We then describe the framework of a generic computer program that can be adapted for use with a broad range of experimental applications. Stimuli are generated in the context of trial events, allowing the display of text messages, the monitoring of subject responses and reaction times, and the inclusion of contingency algorithms. This approach allows direct control and management of computer-generated visual stimuli while utilizing the full capabilities of modern hardware and software systems. The flowchart and source code for the stimulus-generating program may be downloaded from www.psychonomic.org/archive.